Definitions of Density and Unit Volume Supplementary Topic The Concepts of Unit Volume and Density In the main text we talked about the volume and surface area of 3 dimensional objects (such as spheres and discs and cubes). So, why do we need to bother with this in astronomy? What's so important about memorizing a bunch of equations about the volume area of all these objects? Well, the simple answer to these questions is that any object you encounter in astronomy (be it a planet, a star, or a galaxy) will be a 3-dimensional object with some "size" associated with it. This so called "size" can be intuitively thought of as how much space it takes up (i.e., its volume) or in terms of how "large" is it (i.e., its radius or diameter). You mith also wonder what the shape of the object is, how much mass it has, and how is its mass distributed over the space that it occupies? So, whether you like it or not, you will encounter situations where such questions will become important. Two very important concepts to be familiar with are that of unit volume and density. Unit Volume Sometimes we are looking at objects and we need to ask very fundamental questions.

We might not be necessarily interested in how much total space the thing occupies. We might be looking at a part of it, or we might be asking questions such as "how many atoms are there in 1 cm3 of the atmosphere of planet Z"? In such cases we are not asking something about the whole object but only part of the object, or something that we believe - in some approximation - to be a fundamental question to ask about the object. For this reason we define the notion of unit volume. The notion of unit volume is very geometrical and "abstract", but at the same time it is an exteremely simple idea. When we look at a unit volume inside an object we imagine some arbitrary sized cube that is much smaller than the size of the object, but large enough to contain a sufficient "sample" of the object. Density The notion of unit volume can be used to talk about the density of an object. The definition of density is as follows: density = mass/unit volume It has units of "mass" divided by units of "length3", so it is usually given as kg/m3 or g/cm3. Notice how the idea of unit volume enter here.

Ideally, to measure density of an object or of some material, you can imagine going inside the material, taking a small 1cm x 1cm x 1cm sample, and measuring its mass on a scale. The density of the object would then be the measured mass divided by 1 cm3. Sometimes - as you can imagine, in the case of a star for instance - it is impossible to put yourself in the object to make such a measurement. Further complications arise from the fact that real objects - either in our experiences around us or in astronomy - tend to have mass distributed in different amounts in different parts. For instance, imagine your own body. Clearly, the distribution of mass in your body is not uniform! Your bones have a higher density (more mass per unit volume) than your lungs, and so on .... Thus, in reality situations can be quite complicated. But, we are often saved by the fact that - at least at a basic level - we don't care about these complications. We are only interested in average densities. For instance, suppose someone asks you what the density of the sun is. Well, this is a complex question.

For one thing, you have to first worry about the fact that you can't just put yourself in the sun, pick a sample of its mass, weight it, and then calculate the density. You also have to worry about the fact that it might really depend on where you actually took the sample from (from the outer surface of the sun or from the center of the sun)! But ... you can calculate an average density. You can first assume that the sun is roughtly spherical, and so it has a radius R=695,000 km. Then, knowing the formula for the volume of a sphere you can calculate the volume of the sun: V = (4/3) p R3 V = (4/3) (3.1415) (695,000)3 = 1.406 x 1018 km3 Now, from various measurements - which you will learn about in your course - you estimate the mass of the sun to be 1.99 x 1030 kg (or simply, look it up in an astronomy table, like the one at the end of your textbook!).

Then, the average density of the sun is: average density of the sun = total mass of sun/total volume of sun=1.41x1012 kg/(km)3. Using unit converstions you can get this to grams per cubic centimeters. There are 1000 g in a kg and there are 105 cm in one km. Thus, the average density of the sun is 1.41 g/cm3! What Is Density? - Definition & Calculation Question: What is Density? Density Definition A material's density is defined as its mass per unit volume. It is, essentially, a measurement of how tightly matter is crammed together. The principle of density was discovered by the Greek scientist Archimedes . To calculate the density (usually represented by the Greek letter "ρ") of an object, take the mass (m) and divide by the volume (v): ρ = m / v The SI unit of density is kilogram per cubic meter (kg/m3). It is also frequently represented in the cgs unit of grams per cubic centimeter (g/cm3). Using Density One of the most common uses of density is in how different materials interact when mixed together.

Wood floats in water because it has a lower density, while an anchor sinks because the metal has a higher density. Helium balloons float because the density of the helium is lower than the density of the air. When your automotive service station tests various liquids, like transmission fluid, they will pour some into a hydrometer. continue reading below our video 4 Tips for Improving Test Performance The hydrometer has several calibrated objects, some of which float in the liquid. By observing which of the objects float, it can be determined what the density of the liquid is ... and, in the case of the transmission fluid, this reveals whether it needs replaced yet or not. Another important consequence of density is that it allows you to solve for mass and volume, if given the other quantity. Since the density of common substances is known, this calculation is fairly straightforward, in the form: v * ρ = m or m / ρ = v The change in density can also be useful in analyzing some situations, such as whenever a chemical conversion is taking place and energy is being released. The charge in a storage battery, for example, is an acidic solution .

As the battery discharges electricity, the acid combines with lead in the battery to form a new chemical, which results in a decrease in the density of the solution. This density can be measured to determine the battery's level of remaining charge. Density is a key concept in analyzing how materials interact in fluid mechanics, weather, geology, material sciences, engineering, and other fields of physics. Specific Gravity A concept related to density is the specific gravity (or, even more appropriate, relative density ) of a material, which is the ratio of the material's density to the density of water . An object with a specific gravity less than 1 will float in water, while a specific gravity greater than 1 means it will sink. It is this which allows, for example, a balloon filled with hot air to float in relation to the rest of the air. Edited by Anne Marie Helmenstine, Ph.D.​ Mass density - definition of Mass density by The Free Dictionary Mass density - definition of Mass density by The Free Dictionary Related to Mass density: weight density , Specific weight den·si·ty n. pl. den·si·ties 1. The quality or condition of being dense. 2. a.

The quantity of something per unit measure, especially per unit length, area, or volume. b. The mass per unit volume of a substance under specified conditions of pressure and temperature. 3. Computers A measure of the number of bits that can be stored in a given amount of physical space on a storage medium. 4. The number of individuals, such as inhabitants or housing units, per unit of area. 5. The degree of optical opacity of a medium or material, as of a photographic negative. 6. Thickness of consistency; impenetrability. 7. Complexity of structure or content. 8. Stupidity; dullness. (ˈdɛnsɪtɪ) n, pl -ties 1. the degree to which something is filled, crowded, or occupied: high density of building in towns. 2. obtuseness; stupidity 3. (General Physics) a measure of the compactness of a substance, expressed as its mass per unit volume. It is measured in kilograms per cubic metre or pounds per cubic foot. Symbol: ρ See also relative density 4. (General Physics) a measure of a physical quantity per unit of length, area, or volume. See charge density , current density 5.

(General Physics) physics photog See transmission density , reflection density den•si•ty 1. the state or quality of being dense; compactness. 2. stupidity; obtuseness. 3. the average number of inhabitants, dwellings, or the like, per unit of area: a population density of 100 persons per square mile. 4. Physics. mass per unit volume. 5. the degree of opacity of a substance, medium, etc., that transmits light. 6. the relative degree of opacity of an area of a photographic negative or transparency, often expressed logarithmically. 7. a measure of how much data can be stored in a given amount of space on a disk or other computer storage medium. [1595–1605; < Latin] den·si·ty (dĕn′sĭ-tē) A measure of the compactness of a substance. Density is equal to the amount of mass per unit of volume. In general, density increases as pressure increases and temperature decreases.

density compactness - the consistency of a compact solid bits per inch , bpi - a measure of how densely information is packed on a storage medium flux density , flux - (physics) the number of changes in energy flow across a given surface per unit area absorbance , optical density , photographic density , transmission density - (physics) a measure of the extent to which a substance transmits light or other electromagnetic radiation low density , rarity , tenuity - a rarified quality; "the tenuity of the upper atmosphere" relative density - the ratio of the density of something to the density of a standard 2. spatial arrangement , spacing - the property possessed by an array of things that have space between them density 1. tightness , closeness , thickness , compactness , impenetrability , denseness , crowdedness The region has a high population density. 2. mass , body , bulk , consistency , solidity Jupiter's moon Io has a density of 3.5 grams per cubic centimetre. density 1. (= thickness) [of forest, vegetation, fog] → densidad f, lo espeso ; [of population] → densidad f 2.

(Phys) [of material, substance] → densidad f single/double density disk → disco m de densidad sencilla /de doble densidad density [population] → densité f; [housing] → densité f (COMPUTING) single density disk, double-density disk, high-density disk density n → Dichte f; population density → Bevölkerungsdichte f density single-/double-density disk (Comput) → disco a singola / doppia densità dense (dens) adjective 1. thick and close. We made our way through dense forest; The fog was so dense that we could not see anything.

digte كَثيف гъст denso hustý dicht tæt; tyk πυκνός espeso , denso tihe انبوه؛ متراکم؛ غلیظ tiheä dense עָבוֹת घना bujan, gust sűrű lebat þéttur, samþjappaður fitto 濃密な 밀집한 tankus, tirštas biezs; blīvs tebal dicht tett ; tykk, kompakt gęsty ګڼ، خنډ، ټينګ، مزدحم، متراكم، غليظ: احمق denso des густой hustý gost gust tät, kompakt หนาแน่น yoğun , sık 稠密的 густий; щільний کثیف ، گاڑھا dày đặc 稠密的 2. very stupid. He's so dense I have to tell him everything twice.

stompsinnig, dom بَليد، غَليظ الدِّماغ тъп estúpido hloupý, nechápavý schwer von Begriff tykhovedet; dum αργόστροφος corto , torpe , estúpido kõva peaga خنگ؛ کودن tyhmä bête מטומטם मन्दबुद्धि tupoglav, ograničen duhom együgyű bodoh tregur, þunnur stupido 頭の鈍い 우둔한 bukas aprobežots; stulbs bodoh stompzinnig dum , tett tępy احمق estúpido tâmpit тупой nechápavý omejen glup dum, trög โง่ ahmak , kalın kafalı 愚鈍的 дурний, тупий احمق rất ngu ngốc 愚钝的 ˈdensely adverb very closely together. The crowd was densely packed.

dig بِكَثافَه на гъсто densamente hustě dicht tæt πυκνά densamente tihedalt بطور فشرده و متراکم tiiviisti à forte densité בִּצפִיפוּת घना सा gusto, zbijeno sűrűn rapat mjög þétt densamente びっしりと 촘촘히 tankiai biezi; blīvi sangat padat dicht tett gęsto څنګ په څنګ، نږدى densamente compact плотно husto gosto gusto tätt, tät- อย่างหนาแน่น yoğun olarak 密集地 густо; щільно گھنے طور پر đông đúc 密集地 ˈdensity noun 1. the number of items, people etc found in a given area compared with other areas especially if large. the density of the population.

digtheid كَثافَه гъстота densidade hustota die Dichte tæthed πυκνότητα densidad tihedus تراکم؛ انبوهی tiheys densité צפיפות घनत्व zbijenost sűrűség kepadatan þéttleiki densità 密度 밀도 tankumas biezums; blīvums kepadatan dichtheid tetthet , kompakthet gęstość جنگلی densidade densitate плотность hustota gostota gustina täthet ความหนาแน่น yoğunluk 密集度 густота, щільність کثافت mật độ 密集度 2. the quantity of matter in each unit of volume. the density of a gas.

digtheid كَثافَه плътност densidade hustota die Dichte vægtfylde πυκνότητα densidad tihedus چگالی؛ غلظت tiheys densité צפיפות घनत्व gustoća fajsúly kepekatan eðlismassi densità 密度, 濃度 비중 tankis blīvums ketumpatan dichtheid egenvekt , tetthet gęstość غلضت densidade densitate плотность hustota gostota gustina densitet ความหนาแน่น yoğunluk 密度 густина فی اکائی حجم میں موجود کمیت tỷ trọng 密度 density Density, Density Formula, Density of Water | Physics@TutorVista.com The SI unit of density is kilograms per cubic meter or can be written as kg/m3. Liters and metric tons are also used as other types of units.

Some other units are: • Kilograms per liter or can be written as kg/L • Grams per milliliter or can be written as g/mL • Metric tons per cubic meter or can be written as t/m3 * Kilograms per cubic decimeter or can be written as kg/dm3 • Grams per cubic centimeter or can be written as g/cc, gm/cc or g/cm3 • Mega grams per cubic meter or can be written as Mg/m3 In U.S. customary unit’s density can be stated in: • Avoirdupois ounces per cubic inch or can be written as oz/cu in • Slugs per cubic foot • Avoirdupois pounds per cubic inch or can be written as lb/cu in • Pounds per cubic foot or can be written as lb/cu ft • Pounds per cubic yard or can be written as lb/cu yd • Pounds per U.S. liquid gallon or can be written as lb/gal • Pounds per U.S. bushel or can be written as lb/bu There are certain imperial units that are not used these days. How to Find Density? The process of calculating density is quite simple. It is basically the mass divided by volume.

In simple cases we will be provided with two quantities. They are, mass and volume. Convert the given mass of the object in kg if not in this unit. Now convert the volume in cubic meter if not in the given unit. Simply divide mass by volume to find the density. The units of the answer are kg/m3. Similarly other formula for density of solution can be used like $\rho$ = $\sum_{i}\rho_{i}$ for calculating the needed density. For example: If the mass of the substance is 10 kg and the volume is 100 m3 then the density would be calculated as, Density = $\frac{Mass}{Volume}$ = $\frac{10}{100}$ = 0.1 kg /m3 Density Measurement Back to Top If we consider a homogenous body then the density would be equal to total mass divided by total volume. The mass can be measured by any weighing instrument. The volume can be measured using the instrument called Hydrometer. The volume can also be measured using the displacement of the fluid. For a non homogenous body, the measurement process is quite different, the density is dependent on the location where it is measured.

Hence at a particular location density can be found by calculating the density of the tiny volume around that particular location. In this case, the density = $\frac{\Delta m}{\Delta v}$ Hydrometer Back to Top Hydrometer is an instrument used for determining the density of a liquid. It usually consists of a glass float with a long thin stem which is graduated. The glass float is a large hollow bulb which increases the buoyancy so that the hydrometer floats. The narrow stem increases the sensitivity of the hydrometer. The bottom of the hydrometer is made heavier by loading it with lead shots so that it floats vertically. It works on the principle of floatation. It sinks more in a lighter liquid so as to displace more volume of the lighter liquid whose weight is equal to the weight of the hydrometer. Hence, it will sink less in a denser liquid so that it has to displace less volume of the denser liquid whose weight will be equal to the hydrometer. Thus, the lowest density is marked on the top of the stem of a hydrometer and the maximum density is marked at the bottom of the graduated stem. Relative Density Back to Top Specific gravity is another term for relative density.

It is defined as the ratio of the density of a given substance with respect to the density of a given reference material whose density is already known.If we consider Relative density with respect to water then it is termed as Specific gravity. The term "Relative Density" is often used in modern science as compared to relative density. If for a given substance the calculated relative density comes out to be less than 1 then it is said to be less dense than the given reference material. If for a given substance the calculated relative density comes out to be more than 1 then it is said to be more dense than the given reference material. If the reference material to be considered is water and specific density is calculated then a substance with a relative density that is less than one will not sink in water, it will float for sure. For example, if an ice cube is considered it will float as the specific density is less then 1. Some of the prerequisites for calculating the relative density are that the temperature and pressure must be known for both the sample and the reference. Pressure to be used is mostly 1 atm. Temperatures may vary from industry to industry Application of Specific gravity is in industries for obtaining information about the concentration of solutions of various materials such as brines and acids.

It is a dimension less quantity. The formula for Relative Density is RD = $\frac{P_{substance}}{P_{reference}}$. It can have various applications. It can be used for the determination of the density of the substance by using another substance density which is known. It can be used to quantify the Buoyancy. It can be used for finding out the minerals present in the rock by geologists and scientists. It can be used in industries for finding the concentrations of the liquids or chemical present. It can be measured using a Hydrometer. It can be determined using a Pycnometer. There are various other instruments for the measurement of relative density. Air Density Back to Top The density of air is denoted by the Greek letter '$\rho$ called Rho. It is the mass per unit volume of Earth's atmosphere basically. It has its applications in aeronautics and other branches of science. Air density depends upon Altitude, it is inversely proportional to it. It is inversely proportional to Air Pressure. It is dependent on temperature or humidity variances. At sea level and at 15°C air density is approximately 1.225 kg/m3 according to ISA (International Standard Atmosphere).

It can be written as 0.0023769 slugs/ft3. Energy Density Energy density is defined as the amount of energy that is stored in a given system or a given region considering the space per unit volume. • Mostly the extractable energy is quantified because it is the only useful energy. • This means that chemically inaccessible energy is not taken into consideration such as rest mass. • Quantifiable or measurable energy is basically the energy that posses quantified magnitude with some related units. If we take fuels then the density is considered to be a very useful parameter. For example if we consider the effectiveness of hydrogen fuel as compared to gasoline then hydrogen has a higher specific energy than gasoline. If energy storage applications are considered, the energy density basically is the ratio of the total mass of the stored energy and the volume of the storage facility, example, the fuel tank. The higher the energy density of the fuel, the more energy may be stored or transported for the same amount of volume. The energy density per unit mass for a fuel is called the specific energy of that particular fuel. Energy density does not tell anything about energy conversion efficiency or energy that is embodied.

Density of Ice Back to Top Water in frozen or solid state is called ice. It has various forms like flakes etc. The reference material to be considered is water and specific density is calculated then a substance with a relative density that is less than one will not sink in water, it will float for sure. If an ice cube is considered it will float as the specific density is less than 1. • The ice is 8.3% less dense than liquid water approximately. • The value of density is 0.9167 $\frac{g}{cm^{3}}$. • This is at zero degree temperature. • The density of frozen water decreases as the temperature decreases. • It is 0.9340 $\frac{g}{cm^{3}}$ at −180 °C. Volume and Density About Watch and Favorite Watch Watching this resources will notify you when proposed changes or new versions are created so you can keep track of improvements that have been made. Favorite Favoriting this resource allows you to save it in the “My Resources” tab of your account. There, you can easily access this resource later when you’re ready to customize it or assign it to your students.

Volume and Density Density and volume are two common measurements in chemistry. Learning Objective Describe the relationship between density and volume Key Points The volume of a substance is related to the quantity of the substance present at a defined temperature and pressure . The volume of a substance can be measured in volumetric glassware, such as the volumetric flask and the graduated cylinder. Density indicates how much of a substance occupies a specific volume at a defined temperature and pressure. The density of a substance can be used to define the substance. Water is unusual because when water freezes, its solid form (ice) is less dense than liquid water, and thus floats on top of liquid water. Terms Full Text Volume and Density The properties of a material may be described in many ways. Any amount of any substance will have a volume. If you have two containers of water that are different sizes, they each hold a different amount, or volume, of water. The unit for volume is a unit derived from the SI unit of length and is not a fundamental SI measurement. If two water samples have different volumes, they still share a common measurement: the density. Density is another measurement derived from SI basic units. The density of a material is defined as its mass per unit volume.

In this example, each volume of water is different and therefore has a specific and unique mass. The mass of water is expressed in grams (g) or kilograms (kg), and the volume is measured in liters (L), cubic centimeters (cm3), or milliliters (mL). Density is calculated by the dividing the mass by the volume, so that density is measured as units of mass/volume, often g/mL. If both water samples are at the same temperature, their densities should be identical, regardless of the samples' volume. Measurement Tools The measuring cup is a common household utensil used for measuring the volumes of liquids. If you have ever cooked in a kitchen, you have probably seen some sort of measuring cup, which allows the user to measure liquid volumes with reasonable accuracy . The measuring cup expresses liquid volume in the standard SI units of liters and milliliters. Most American measuring cups also measure liquid in the older system of cups and ounces. Volumetric Glassware Scientists who work in a laboratory must be familiar with typical laboratory glassware, often called volumetric glassware. These may include beakers, a volumetric flask, an Erlenmeyer flask, and a graduated cylinder.

Each of these containers is used in a laboratory setting to measure liquid volumes for different purposes. Glassware, such as these beakers, is commonly used in a laboratory setting to conveniently measure and separate different volumes of liquids. Density of Water Different substances have different densities, so density is often used as a method to identify a material. Comparing the densities of two materials can also predict how substances will interact. Water is used as the common standard to substances, and it has a density of 1000 kg/m3 at Standard Temperature and Pressure (called STP). Using Water as a Density Comparison When an object is placed in water, the object's relative density determines whether it floats or sinks. If the object has a lower density than water, it will float to the top of the water. An object with a higher density will sink. For example, cork has a density of 240 kg/m3, so it will float. Air has a density of approximately 1.2 kg/m3, so it rises immediately to the top of a water column.

The metals sodium (970 kg/m3) and potassium (860 kg/m3) will both float on water, while lead (11,340 kg/m3) will sink. Is the crown made of pure gold? An ancient Greek king needs to know if he's been cheated by a goldsmith. He summons Archimedes, who decides to use density to determine the metal. But how can he determine the volume of the crown? Liquids tend to form layers when added to water. The sugar alcohol glycerol (1,261 kg/m3) will sink into the water and form a separate layer until it is thoroughly mixed (glycerol is soluble in water). Vegetable oil (approx. 900 kg/m3) will float on water, and no matter how vigorously mixed, will always return as a layer on the water surface (oil is not soluble in water). The Variable Density of Water Water itself is a complicated and unique molecule . Even if the pressure is consistent, water's density will change based on the temperature. Recall that the three basic forms of matter are solid, liquid and gas (ignore plasma for the time being).

As a rule of thumb, almost all materials are more dense in their solid or crystalline form than in their liquid form; place the solid form of almost any material on the surface of its liquid form, and it will sink. Water, on the other hand, does something very special: ice (the solid form of water) floats on liquid water. Look carefully at the relationship between water's temperature and its density. Beginning at 100 °C, the density of water steadily increases, as far as 4 °C. At that point, the density trend reverses. At 0 °C, water freezes to ice and floats. This table lists the densities of water at different temperatures and constant pressure. The implications of this simple fact are enormous: when a lake freezes, ice crusts at the surface and insulates the liquid below from freezing , while at the same time allowing the colder water (with a temp of approx. 4 °C and a high density) to sink to the bottom. If ice did not float, it would sink to the bottom, allowing more ice to form and sink, until the lake froze solid!

Scuba divers and swimmers often encounter these water temperature gradients, and they might even encounter a water layer at the very bottom of a lake with a temperature of approximately 4 °C. That's just about as cold as the lake will get at the bottom; as soon as the water gets colder, the liquid water becomes less dense and rises. Mass density | Article about Mass density by The Free Dictionary Mass density | Article about Mass density by The Free Dictionary Related to Mass density: weight density , Specific weight density, ratio of the mass mass, in physics, the quantity of matter in a body regardless of its volume or of any forces acting on it. The term should not be confused with weight, which is the measure of the force of gravity (see gravitation) acting on a body. ..... Click the link for more information. of a substance to its volume, expressed, for example, in units of grams per cubic centimeter or pounds per cubic foot. The density of a pure substance varies little from sample to sample and is often considered a characteristic property of the substance. Most substances undergo expansion when heated and therefore have lower densities at higher temperatures. Many substances, especially gases, can be compressed into a smaller volume by increasing the pressure acting on them.

For these reasons, the temperature and pressure at which the density of a substance is measured are usually specified. The density of a gas is often converted mathematically to what it would be at a standard temperature and pressure (see STP). Water is unusual in that it expands, and thus decreases in density, as it is cooled below 3.98&degC; (its temperature of maximum density). Density often is taken as an indication of how "heavy" a substance is. Iron is denser than cork, since a given volume of iron is more massive (and weighs more) than the same volume of cork. It is often said that iron is "heavier" than cork, although a large volume of cork obviously can be more massive and thus be heavier (i.e., weigh more) than a small volume of iron. See specific gravity specific gravity, ratio of the weight of a given volume of a substance to the weight of an equal volume of some reference substance, or, equivalently, the ratio of the masses of equal volumes of the two substances. ..... Click the link for more information. . Density The mass per unit volume of a material.

The term is applicable to mixtures and pure substances and to matter in the solid, liquid, gaseous, or plasma state. Density of all matter depends on temperature; the density of a mixture may depend on its composition, and the density of a gas on its pressure. Common units of density are grams per cubic centimeter, and slugs or pounds per cubic foot. The specific gravity of a material is defined as the ratio of its density to the density of some standard material, such as water at a specified temperature, for example, 60°F (15.6°C), or, for gases the basis may be air at standard temperature and pressure. Another related concept is weight density, which is defined as the weight of a unit volume of the material. See Mass , Weight density 1. Symbol: ρ. The mass per unit volume of a body or material. The mean density of a celestial body is its total mass divided by its total volume. A wide variation in densities is found in the Universe, ranging from about 10–20 kg m–3 for interstellar gas to over 1017 kg m–3 for neutron stars.

The mean density of matter in the Universe is of the order of 10–27 kg m–3. 2. The number of electrons, ions, or other particles per unit volume. Density A planning or zoning unit of measurement of the ratio between buildings per acre, or occupants per gross square foot of floor area, according to the type of zoning for that particular area under consideration, such as commercial residential, rural, and the like. Density in textiles, the content of fibrous material per unit volume. The density of a weave determines the strength and appearance of the fabric. It is usually expressed by the number of warp threads per unit of width and the number of filling threads per unit of length—that is, the ratio of absolute density along warp and filling. When the linear density (fineness) of the threads varies, a ratio of relative density is used, expressed by a filling coefficient—linear, surface, or volume—representing the relationship of the linear measurements of surface or volume to the overall width, length, surface, or volume of a unit of material. The relative density is determined basically by the type of fiber interlacing used in the weave.

For a weave of normal density, about 40 or 50 percent of the volume of a fabric consists of fibrous material. density Chemistry Tutorial : Density Calculations Density Calculations Density is defined as mass per unit volume . Density can be calculated using the formula: d = m ÷ v where d = density, m = mass, v = volume The greater the density, the more mass per unit volume. The unit of density derived from SI units is kilograms per cubic meter, kg/m3 or kgm-3. More commonly, densities are given in g/mL (gmL-1) or g/cm3 (gcm-3 or g/cc). Density is a characteristic property of pure substances so density can help identify a particular pure substance. Densities of Some Pure Substances Pure Substance 0.0013 In general metals are more dense than non-metals*. For example, at 25oC the density of metallic lead is 11.4g/mL while the density of non-metallic sulfur is only 2.0g/mL.

The mass of 1mL of lead would be 11.4g, while the mass of 1mL of sulfur is only 2.0g In general, solids are more dense than liquids which are more dense than gases**. For example, at 25oC, solid sulfur has a density of 2.0g/mL, liquid water has a density of 1.0g/mL and gaseous oxygen has a density of 0.0013g/mL. * There are quite a few exceptions, especially the Group I (alkali metals) which have unusually low densities compared with other metals. **Note that mercury is an exception, it is a very dense liquid. Density Calculations density = mass ÷ volume This equation can be re-arranged in order to calculate mass or volume given the density of a substance: mass = density x volume volume = mass ÷ density Check for consistency in units: If density is given in g/mL then the mass must be in grams and the volume in milliltres. If the density is given in g/cm3 then the mass must be in grams and the volume in cubic centimetres.

Examples of Calculations Using Densities Calculate the density of a ruby which has a volume of 1.6 cm3 and a mass of 6.7g. density = mass ÷ volume density = 6.7 ÷ 1.6 = 4.2 g/cm3 Calculate the density of a liquid which has a volume of 28mL and a mass of 26.4g density = mass ÷ volume density = 26.4 ÷ 28 = 0.94 g/mL Beeswax has a density of 0.96 g/cm3 at 25oC and 1atm pressure. Calculate the mass of 5 cm3 of beeswax. density = mass ÷ volume So mass = density x volume mass = 0.96 x 5 = 4.8g Milk has a density of 1.03 g/mL at 25o and 1atm pressure. Calculate the mass of 1L of milk.

density = mass ÷ volume So mass = density x volume Convert 1L to millilitres: volume = 1L x 1000mL/L = 1000mL mass = 1.03g/mL x 1000mL = 1030g (=1.030kg) At 25o and 1atm pressure, diamond has a density of 3.5 g/cm3. Calculate the volume of 0.5g of diamond. density = mass ÷ volume DENSITY AND PRESSURE DENSITY AND PRESSURE The density of a material is defined as the mass per unit volume.

densityï¿½ =ï¿½ rï¿½ =ï¿½ mass/Volumeï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ (the Greek letter rho) ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ The units areï¿½ï¿½ï¿½ï¿½ ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½=ï¿½ kilograms/meter3ï¿½ =ï¿½ kg/m3 Itï¿½s a measure of how tightly the atoms of a material are packed.ï¿½ï¿½ It has nothing to do with the hardness of the material.

19300 ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ The specific gravity of a material is the ratio of its density to that of water.ï¿½ For example, the specific gravity of aluminum would be 2.7.ï¿½ This number is dimensionless. ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ The pressure, P, is defined as the ratio of force to area: ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ The units of pressure are:ï¿½ Newtons/meter2ï¿½ = N/m2 = Pascalsï¿½ =ï¿½ Pa Example: ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ A hammer supplies a force of 700 N.ï¿½ The hammer head has an area of 7.1 x 10-4 m2.ï¿½ What is the pressure?

ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Pï¿½ =ï¿½ F/A ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿

½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Pï¿½ =ï¿½ (700 N/7.1 x 10-4 m2) ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Pï¿½ =ï¿½ 9.86 x 105ï¿½ N/m2 ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿

½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Pï¿½ =ï¿½ 9.86 x 105ï¿½ Pa VARIATION OF PRESSURE WITH DEPTH ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ If a fluid is at rest, then all points at the same depth must be at the same pressure (otherwise it would be moving!).ï¿½ However the pressure WILL vary with depth: it will have the weight of the fluid on top of it.

P = pressure,ï¿½ Po = pressure due to the air (atmospheric pressure) ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Because the fluid is at rest, the net force will beï¿½ _________ ?

ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ So we can write: ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Fnetï¿½ =ï¿½ 0 ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï

¿½ï¿½ï¿½ï¿½ï¿½ï¿½ ï¿½ï¿½ PA ï¿½ mg ï¿½ PoAï¿½ =ï¿½ 0 However we know that:ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Massï¿½ =ï¿½ density x volumeï¿½ =ï¿½ density x (area x height) ï¿½ï¿½ï¿½ï¿½ Mï¿½ =ï¿½ rVï¿½ =ï¿½ rAhï¿½ï¿½ï¿½ So we can substitute: ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ PA ï¿½ (rAh)g - PoAï¿½ =ï¿½ 0 cancel out the Area

, A: ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ P ï¿½ (rh)g - Poï¿½ =ï¿½ 0 and the pressure at any depth will be: ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Pï¿½ =ï¿½ Po + rgh In words this says: the pressure at a depth ï¿½hï¿½ will be the atmospheric pressure(

14.7 lbs/in2) + (rgh) Exampleï¿½ 1:ï¿½ Calculate the pressure at a depth of 3.0 m in a swimming pool.

rwaterï¿½ =ï¿½ (1000 kg/m3) Pï¿½ =ï¿½ Po + rgh Pï¿½ =ï¿½ (1.013 x 105 Pa)ï¿½ +ï¿½ (1000 kg/m3)(9.8 m/s2)(3.0 m) Pï¿½ =ï¿½ (1.013 x 105 Pa)ï¿½ +ï¿½ 2.94 x 104ï¿½ Pa Pï¿½ =ï¿½ 1.31 x 105 Paï¿½ =ï¿½ 131,000 Paï¿½ =ï¿½ 19 lb/in2. at a depth of 30 m (100 ft) the pressure would be:ï¿½ ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 57 lb/in2.

at a depth of 300 m (1000 ft) the pressure would be: ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 440 lb/in2. Example 2: You are a CIA operative in the jungles of Burma escaping from a rebel force.ï¿½ You see a stream and reeds and you cut off a reed, jump into the stream and lie about half a meter under water breathing thru the reed.ï¿½ Can you breathe? Answer:ï¿½ letï¿½s determine the pressure on your chestï¿½ Pï¿½ =ï¿½ rgh Pï¿½ =ï¿½ (1000 kg/m3)(9.8 m/s2)(0.5 m) Pï¿½ =ï¿½ 4900ï¿½ Paï¿½ =ï¿½ 0.71 psi If your chest is 12 in. by 12 in.ï¿½ (approximately) then the area = 144 sq. in.

Force = Pressure x Areaï¿½ =ï¿½ 0.7 psiï¿½ xï¿½ 144 sq.in.ï¿½ =ï¿½ 100 pounds So, yeh, probablyï¿½but donï¿½t go much deeper! PASCALï¿½S PRINCIPLE:ï¿½ Pressure applied to an enclosed fluid is transmitted equally to all points of the fluid (and therefore to all walls of the vessel containing the fluid) ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ What good is this?ï¿½ ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ We can turn this phenomenon to our advantage if we alter the areas exposed to equal pressures: as in an hydraulic lift: Since the pressure must be the same everywhere: Pat 1ï¿½ =ï¿½ Pat 2 Density | Units of Measurement Wiki | Fandom powered by Wikia Edit The higher an object's density, the higher its mass per volume . The average density of an object equals its total mass divided by its total volume.

A denser object (such as iron ) will have less volume than an equal mass of some less dense substance (such as water ). The SI unit of density is the kilogram per cubic meter ( kg · m-3 ) where ρ is the object's density (measured in kilograms per cubic meter ) m is the object's total mass (measured in kilograms ) V is the object's total volume (measured in cubic meters ) Under specified conditions of temperature and pressure, density of a fluid is defined as described above. Definitions Edit However, the density of a solid material can be different, depending on exactly how it is defined. Take sand for example. If you gently fill a container with sand, and divide the mass of sand by the container volume you get a value termed loose bulk density . If you took this same container and tapped on it repeatedly, allowing the sand to settle and pack together, and then calculate the results, you get a value termed tapped or packed bulk density. Tapped bulk density is always greater than or equal to loose bulk density. In both types of bulk density, some of the volume is taken up by the spaces between the grains of sand.

Also, in terms of candy making, density is affected by the melting and cooling processes. Loose granular sugar , like sand, contains a lot of air and is not tightly packed, but when it has melted and starts to boil, the sugar loses its granularity and entrained air and becomes a fluid. When you mold it to make a smaller, compacted shape, the syrup tightens up and loses more air. As it cools, it contracts and gains moisture, making the already heavy candy even more dense. A more theoretical definition is also available. Density can be calculated based on crystallographic information and molar mass: where Edit Density in terms of the SI base units is expressed in terms of kilograms per cubic meter (kg·m-3). Other units fully within the SI include grams per cubic centimeter (g·cm-3) and megagrams per cubic meter (Mg·m-3). Since both the liter and the tonne or metric ton are also acceptable for use with the SI, a wide variety of units such as kilograms per liter (kg·L-1) are also used. In Imperial units or U.S.

customary units , the units of density include pounds per cubic foot (lb/ft³), pounds per cubic yard (lb/yd³), pounds per cubic inch (lb/in³), ounces per cubic inch (oz/in³), pounds per gallon (for U.S. or imperial gallons) (lb/gal), pounds per U.S. bushel (lb/bu), in some engineering calculations slugs per cubic foot, and other less common units. The maximum density of pure water at a pressure of one standard atmosphere is 999.972 kg·m-3; this occurs at a temperature of about 3.98 °C (277.13 K). Measurement of density A common device for measuring fluid density is a pycnometer . A device for measuring absolute density of a solid is a gas pycnometer . Highest density The most dense naturally occurring substance on Earth is iridium , at about 22650 kg·m-3. A table of densities of various substances: Substance

Question: What is defined as the mass per unit volume, of a material?
Answer: DENSITY